Acrocinus longimanus (Linnaeus, 1758)
POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
LAMIINAE Latreille, 1802
Native to Central and South America, from Mexico to Brazil and Uruguay, as well as various Caribbean islands, and still locally common throughout much of this range despite widespread environmental abuse, this is among the largest and most spectacular of the tropical longhorns. The striking patterns and colours exhibited by both sexes are ornate and appealing but they also serve to protect the beetles as they are surprisingly cryptic against decaying and fungoid trunks and branches. The species is associated with tropical forests and is dependent on decaying broadleaf trees for its development, an increasingly tenuous lifestyle as the wood-boring larvae may take several years to become fully-grown. Adults are active both by day and at night, they fly readily about the canopy and are strongly attracted to sap on which they feed. The greatly elongated forelegs of males are used for defending territory against rival males and are important in attracting females; antennal length denotes dominance and males with the longest antennae will ‘claim’ an area of decaying wood and defend it against rivals until a female arrives. The males powerful mandibles are also used in fighting and are easily capable of removing a rivals legs and antennae, but fights are usually brief and unsuccessful males are quickly removed from the arena. These unsuccessful males will fly off, either to find their own territory or to challenge others, while successful males will generally mate with multiple females. The beetles rarely occur in numbers and most encounters are of single specimens; they spend much of their time on trunks or branches which are covered with fungus and lichens etc., but they become very active when another beetle is in the vicinity. Mating occurs soon after a female arrives in a male ‘territory’, and following this the pair will remain together for some time. Pregnant females chew small cavities into dead wood or fungi and insert batches of eggs; typically between 10 and 20 over a period of 2 or 3 days, all the while being guarded by the male who will leave soon after this is completed. Both adults and larvae are widely polyphagous; they feed on wood, fungi, bark and sap as well as decaying plant material and animal droppings, depending on their environment, and larvae can change their diet as required. Upon emerging the larvae bore into bark or wood and produce random galleries to a depth of 13
Acrocinus longimanus ♀
cm or so Development is rapid and under good conditions they are fully grown within 7 or 8 months, although this can be greatly extended according to nutrition etc., at which time they pupate in situ, and adults emerge from the wood up to 4 months later via the larval galleries. Thus the species is annual, or at least mostly so, and adults may live for six months or more. Adults are very sensitive to sap released from moribund trees just before they fall over and so they are often among the first beetles to colonize freshly-fallen timber. This rapid colonization also benefits other species; the elytral pits are usually home to numbers of various mites, and breeding populations of pseudo scorpions often live beneath the elytra, with males venturing out to ‘wrestle’ for mating rights on the elytral surface. While both males and female beetles are mostly diurnal, they are strongly attracted to light traps and will remain active for as long as the lights are shining, much to their cost. The species is classified as vulnerable over much of its range, and deforestation is the main cause of concern, but specimens are also taken in large numbers by collectors who then sell them as pets or mount them in frames etc., a quick look online will soon produce many such ornaments, and despite various campaigns to protect this species, the carnage continues.
The large size and striking dorsal pattern comprising orange (or red or pink), yellow, greenish and black streaks and patches arranged symmetrically across the body, and even on the legs, are very distinctive and so the species should be instantly recognizable. The largest adults are said to measure up to 8 cm, and males are particularly impressive due to their forelegs which can be much longer than the body. Females, though hardly less impressive, have shorter forelegs, smaller mandibles and lack the cephalic horns seen in males. It really is worth taking some time to study the morphology of this species (although in this respect it is hardly any more amazing than many other tropical longhorns), especially features such as the punctures on the elytral surface and the teeth on the humeri and apices, the lateral pronotal teeth and the structure of the legs.